The flowering responses of crop and pasture species in Australia I. Factors affecting development in the field of Lolium species (L. rigidum Gaud., L. perenne L., L. multiflorum Lam.)

1966 ◽  
Vol 17 (6) ◽  
pp. 821 ◽  
Author(s):  
Y Aitken
Keyword(s):  
Early Summer ◽  
Winter Temperature ◽  
Flower Initiation ◽  
Early Group ◽  
Lolium Rigidum ◽  
Factors Affecting ◽  
Cold Requirement

Cultivars of three species of ryegrass (Lolium rigidum Gaud., L. perenne L., and L. multiflorum Lam.) were grown in the open and in the glasshouse at Melbourne (lat. 38° S.), with additional lighting and vernalization when required. They were sown at different times through the year and were compared for times of flower initiation and heading and for leaf numbers to heading. They included two early cultivars (Wimmera, Kangaroo Valley), four mid-season ones (Victorian, Grasslands Ruanui, Tasmanian No. 1, Grasslands Paroa), and one late one (S.23) from England. For all cultivars studied, some cold was required for flower initiation, while long days hastened it somewhat; development between initiation and heading was hastened by both warmth and long days. The early group with a small cold requirement initiated in winter and spring and headed in spring and summer. The mid-season group with a larger cold requirement initiated only in spring, and headed in mid spring to early summer. The late cultivar headed scantily or not at all, the winter temperature being too high for initiation.

Flower initiation in relation to maturity in crop plants. I. Flower initiation in relation to maturity in some Australian oats (Avena spp.)

1961 ◽  
Vol 12 (3) ◽  
pp. 371 ◽  
Author(s):  
Y Aitken
Keyword(s):  
High Temperatures ◽  
Low Temperatures ◽  
Subterranean Clover ◽  
Late Summer ◽  
Crop Plants ◽  
Leaf Number ◽  
Flower Initiation ◽  
Early Group ◽  
Wide Range ◽  
Cold Requirement

The description of oat varieties as early, mid, and late depends mainly on differences in their time of flower initiation. Flower initiation has been studied in varieties grown in southern Australia and ranging in maturity from first early to late. The time to flower initiation was found to depend greatly on the variety�s response to photoperiod and temperature. In all groups but the first early one, initiation was hastened by lengthening photoperiod and reducing temperature. The later the variety, the greater was the effect. Early varieties are those in which initiation occurs at a low leaf number over a wide range of photoperiods and temperatures. Late varieties result from initiation at a high leaf number, the delay compared with early varieties being due to sensitivity to high temperatures and to short photoperiods. These are the conditions prevailing after late summer and autumn sowings. Late varieties mature early in the field when grown either at low temperatures (below 50�F), or at slightly higher temperatures (below 60�F) and intermediate photoperiod. This is similar to the reaction of variety Clare in the second early group of' subterranean clover. Very late varieties of oats, similar to winter wheats which have a pronounced cold requirement for initiation, are not yet present in Australia.

Factors affecting the response ofLongitarsus jacobaeae(Coleoptera: Chrysomelidae) to upwind plant odours

1996 ◽  
Vol 86 (3) ◽  
pp. 307-313
Author(s):  
Zhi-Qiang Zhang ◽  
Peter B. McEvoy
Keyword(s):  
Wind Tunnel ◽  
Host Plants ◽  
Local Density ◽  
Flea Beetle ◽  
Late Summer ◽  
Developmental State ◽  
Early Summer ◽  
Directed Movement ◽  
Factors Affecting ◽  
Plant Odours

AbstractFactors (developmental state, starvation time, host local density and host distance from insects) affecting the response of the ragwort flea beetle,Longitarsus jacobaeae(Waterhouse), to upwind plants of tansy ragwort,Senecio jacobaeae(Compositae), were examined in a wind tunnel. There was seasonal variation in beetle response to host odours. Individuals collected during spring and early summer (6 May to 14 July 1993) showed directed movement toward the upwind plants. However, individuals collected in mid-summer (23 July 1993) showed no significant response to upwind host plants and walked randomly in the wind tunnel. Individuals collected during late summer to autumn (4 August to 23 October 1994) once again showed response to upwind plants, whereas those collected in winter (January 1994) walked randomly in the wind tunnel. The absence of beetle response to plant odours coincided with potential summer aestivation and winter ‘hibernation’. For spring and early summer beetles that responded to plant odours, the strength of the response did not change significantly with the number of plants (1, 2, 4 or 6) presented upwind in the tunnel nor with the starvation time (2, 6, 10, 12, 24 or 36 h) of the tested beetles, and these patterns were consistent for male and female beetles. Individuals responded to plants from a distance of 60 and 300 cm. The speed of movement, similar for males and females, increased slightly asL. jacobaeaeoriented more directly toward host plants.

Flower initiation in pasture legumes. I. Factors affecting flower initiation in Trifolium subterraneum L.

1955 ◽  
Vol 6 (2) ◽  
pp. 211 ◽  
Author(s):  
Y Aitken
Keyword(s):  
Low Temperature ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Cold Period ◽  
Effect Of Temperature ◽  
Flower Initiation ◽  
Temperature Level ◽  
Factors Affecting ◽  
Pasture Legumes ◽  
Precise Knowledge

The value of the annual legume Trifolium subterraneum L. (subterranean clover) in Australian agriculture warrants more precise knowledge of factors affecting flowering and prolific seeding. The effect of temperature and photoperiod on flower initiation in early and later flowering varieties has been investigated in an effort to determine the geographical limits of the use of subterranean clover in Australia. At any time of sowing, the length of the growing season of a variety depends greatly on the variety's response to the temperature level and to the photoperiod of the first few weeks after germination. In all varieties of subterranean clover so far examined flower initiation is accelerated by a period of low temperature. In the later varieties, flower initiation is prevented by an insufficient period of low temperature. The length of the necessary cold period is shortened under longer photoperiod. Early varieties are early flowering because they do not require so long a cold period or so low a temperature as late varieties.

The effect of vernalization on the heading of Wimmera ryegrass (Lolium rigidum) and on five cultivars of perennial ryegrass (Lolium perenne)

1964 ◽  
Vol 4 (15) ◽  
pp. 352 ◽  
Author(s):  
JH Silsbury
Keyword(s):  
Lolium Perenne ◽  
Perennial Ryegrass ◽  
Cold Treatment ◽  
Continuous Light ◽  
Leaf Number ◽  
Lolium Rigidum ◽  
Artificial Seed ◽  
Mediterranean Origin ◽  
Wimmera Ryegrass ◽  
Cold Requirement

The responses of annual and perennial ryegrass to 0, 6, and 12 weeks artificial seed vernalization were determined by recording the percentages of plants heading and the leaf numbers at heading for populations of 40 plants grown in a glasshouse under continuous light. All plants of the annual L. rigidum headed without vernalization but the vernalized plants headed at a much lower leaf number than did the unvernalized controls. At least six weeks of cold treatment were needed for complete induction of the five cultivars of L. perenne examined. The vernalization responses of cultivars of Mediterranean origin were similar to those of the Australian Colac. It was shown that late heading in L. perenne is not always associated with a large cold requirement and it is suggested that photoperiod may be an important factor controlling heading of ryegrass in southern Australia.

Post-fire ephemerals and spinifex-fuelled fires: a decision model for bilby habitat management in the Tanami Desert, Australia

2007 ◽  
Vol 16 (6) ◽  
pp. 741 ◽  
Author(s):  
Richard Southgate ◽  
Susan Carthew
Keyword(s):  
Habitat Suitability ◽  
Decision Model ◽  
Habitat Management ◽  
Fire History ◽  
Spatial Databases ◽  
Ground Cover ◽  
Weather Conditions ◽  
Early Summer ◽  
Annual Rainfall ◽  
Factors Affecting

Seed from post-fire ephemeral plants like Yakirra australiense can form an important component of the diet of the bilby, a threatened arid-dwelling bandicoot. An investigation was conducted to determine the factors affecting the production of Yakirra and fire reoccurrence in the Tanami Desert. A simple decision model was produced to assist managers decide where and when to burn and what to expect regarding Yakirra australiense growth following fire and rainfall. The information used in the model may be derived from existing spatial databases that document rainfall and fire history and could be used to map broad-scale temporal change in total vegetation cover and components of habitat suitability for the bilby. The season and magnitude of rainfall and time-since-fire were the most important variables in the production of Yakirra seed. Rainfall >300 mm within a 2-month period of intense-complete burns could result in >5% Yakirra cover, and >100 mm was required for >1% cover. Negligible Yakirra cover occurred in adjacent long-unburnt plots. Total ground cover and spinifex cover varied substantially in relation to mean annual rainfall, but not in relation to substrate type. Long-unburnt spinifex cover was mostly too sparse to carry a fire in the southern part of the Tanami and the growth of non-spinifex vegetation would be necessary to boost fuel loads sufficiently to carry a fire. Generally, more than 41% cover was required to carry a fire but this was also dependent on weather conditions. Managers should aim to burn in late spring or early summer to improve Yakirra production. Fire management to enhance habitat suitability for the bilby would be of most benefit in the northern part of the Tanami Desert where growth rate of vegetation is greater and there is little existing fire age heterogeneity.

Influence of moonlight on nightjars’ vocal activity: a guideline for nightjar surveys in Europe

Biologia ◽  
2015 ◽  
Vol 70 (7) ◽  
Author(s):  
Luís Reino ◽  
Miguel Porto ◽  
Joana Santana ◽  
Tomasz S. Osiejuk
Keyword(s):  
Survey Methods ◽  
Mediterranean Area ◽  
Lunar Cycle ◽  
Early Summer ◽  
Factors Affecting ◽  
Moon Phases ◽  
Vocal Behaviour ◽  
Bird Survey ◽  
Southern Portugal ◽  
Vocal Activity

AbstractStrictly nocturnal or crepuscular habits on birds are restricted to a very limited number of species such as nightjars. Physiological skills of these species combined with ecological and behavioural adaptations provide them the ability to colonise a less competitive niche. Nightjars’ nocturnal ecological adaptations have been largely neglected on bird survey methods, which can bias the obtained results. Here, we studied the factors affecting vocal activity of two nightjar species, red-necked nightjar Caprimulgus ruficollis and European nightjar C. europaeus in a Mediterranean area of southern Portugal by modelling observed vocal activity of both species as a function of astronomic variables, particularly moon phase and day of the year. Red-necked nightjar vocal behaviour was positively associated with brighter moon phases and springtime, whereas European nightjar was only influenced by the season, being more active in the summer. This reveals the importance of light conditions on vocal activity of the former species. We suggest that specifically designed field surveys for these species should be preferentially conducted during brighter nights, when the lunar cycle is close to full moon. Furthermore, positive contacts with birds are maximized from late spring to early summer, at least for the red-necked nightjar.

Climatic determinants of introduced Sitka spruce in Hiiumaa Island, Estonia

2019 ◽  
Vol 25 (1) ◽  
pp. 161-167
Author(s):  
Alar Läänelaid ◽  
Samuli Helama
Keyword(s):  
Norway Spruce ◽  
Tree Ring ◽  
Sitka Spruce ◽  
Early Summer ◽  
Winter Temperature ◽  
Moisture Regime ◽  
Growth Responses ◽  
Growth Variability ◽  
Tree Ring Data ◽  
Winter Temperatures

Tree-ring records of Sitka spruce growing in Hiiumaa (Estonia) were investigated to illustrate their growth variability and its climatic determinants. A chronology comprising ring-width series of eight big individuals from the Suuremõisa forest park was correlated with local climatic records. The growth variability of this species introduced to Hiiumaa was statistically explained profoundly by winter temperature and early-spring precipitation. Comparisons were also made with local tree-ring data of Norway spruce. Interestingly, both the native and non-native species responded positively to precipitation in June and negatively to precipitation in April. Previous studies have shown that the winter temperature response, demonstrated here for Sitka spruce, is found as Norway spruce growth responses in eastern Estonia, whereas in western Estonia the growth of the latter species is more clearly connected, similar to our findings, to early-summer precipitation. These findings indicate that while the both spruce species remain sensitive to spring/summer moisture regime, the growth of Sitka spruce may actually be less tolerate to winter temperatures, as evident here in western Estonia where the winters may likely be milder than in eastern Estonia. Common to Sitka spruce results from Hiiumaa, tree-ring data representing conspecific native populations from north-west North American sites indicated positive responses to mid-winter temperatures. Based on these results, low winter temperatures and early-summer droughts may both threaten the survival of the remnant individuals of this species in Hiiumaa.

scholarly journals Effects of Cold and Photoperiod on Flowering of Several Herbaceous Perennial Species

HortScience ◽  
1996 ◽  
Vol 31 (4) ◽  
pp. 581b-581
Author(s):  
Erik S. Runkle ◽  
Royal D. Heins ◽  
Arthur C. Cameron ◽  
William H. Carlson
Keyword(s):  
Cold Treatment ◽  
Continuous Light ◽  
Flower Initiation ◽  
Perennial Species ◽  
Cold Response ◽  
Long Day ◽  
Before And After ◽  
Cold Requirement ◽  
Incandescent Lamps ◽  
Herbaceous Perennial

Thirty herbaceous perennial species were treated at 5°C for 0 or 15 weeks. Critical photoperiods for flower initiation and development with and without a cold treatment were determined. Photoperiods were 10, 12, 13, 14, 16, or 24 hours of continuous light or 9 hours plus a 4-hour night interruption. Continuous photo-periodic treatments consisted of 9-hour natural days extended with light from incandescent lamps. Species were categorized into nine response types based on the effects of cold and photoperiod on flowering. Plants had three flowering responses to cold treatment: obligate, facultative, or none. The perennials were obligate long-day, facultative long-day, or day-neutral plants. For example, Campanula carpatica `Blue Clips' had no response to cold and was an obligate long-day plant requiring photoperiods of 16 hours or longer or night interruption for flowering. Rudbeckia fulgida `Goldsturm' had a facultative response to cold and required photoperiods of 14 hours or longer or night interruption for flowering. Veronica longifolia `Sunny Border Blue' had an obligate cold requirement and was day-neutral. Some species responded differently to photoperiod before and after cold. Leucanthemum ×superbum `Snow Cap' flowered as an obligate long-day plant without cold and as a facultative long-day plant after cold. Response categories are discussed.

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